In the oil and gas industry a "blow out" occurs when there is an uncontrolled flow of gas and oil from a well. A device used to prevent the uncontrolled release of gas or oil from a well while drilling is in progress is called a "blow out preventor" or "BOP". The BOP is attached by means of a flange to a casing bowl welded to the top of the well casing. If, for any reason, the BOP should fail to function an uncontrolled flow of oil and gas will occur. Often this uncontrolled flow of gas and oil is ignited by a spark and the ensuing fire reduces on surface equipment to twisted metal which hinders attempts to regain control of the flow. Personnel fighting the fire can readily extinguish the fire, however, there is an extreme danger of the oil and gas being reignited unless the flow is controlled. Before the flow can be controlled, the casing is cut off below the casing bowl to remove the faulty BOP and another and casing bowl is welded in place and a new BOP installed. With gas and oil flowing from the well this is a very difficult and dangerous procedure.